Washington State University has a great site called Ask Dr. Universe. The website invites students to submit a question, or look though questions asked by other children. Questions are categorized so that children can explore topics based on their curiosity.
You can use this website to spark children’s curiosity or to create and ask a question of an expert. This questions may derive from an individual student investigation or a whole class discussion. When children submit a question to an expert, they have to type in an email address. With younger students, e-mail replies are best filtered through the teacher’s email account. A feature that I really like about this website is that, instead of typing a question, students can upload their question with a video.
Here’s a short, official, video highlighting the tool: